male releases more effective than the procedure outlined above might be developed. 

 Preliminary calculations indicate that the use of nonresidual insecticide treatments 

 interspersed with the release of sterile males would be the most efficient integrated 

 program. Such a program would take full advantage of the biology and mating behavior 

 of the insect. In such integrated programs the development and use of a strain resistant 

 to the insecticide employed would be a great advantage over a normal susceptible strain. 

 The writer believes that there is every reason to regard the sterile male method as a 

 feasible approach to boll weevil eradication. Any measure that conceivably could 

 achieve eradication of a pest at a cost less than the annual losses, would seem to 

 justify adequate research effort by scientists. 



Tobacco Hornworm 



Significant Features of the Insect That Have a Bearing on the Possible 

 Use of Sterile Insects for Population Control 



The tobacco hornworm ( Protoparce sexta (Johannson)) and the tomato hornworm 

 ( Protoparce quinquemaculata (Haworth)) are major pests of tobacco and tomatoes. For 

 the purpose of this report, only the tobacco hornworm, the more important and the more 

 abundant of the two species, will be considered, although both species would have to be 

 dealt with in any effort to protect tobacco from hornworms. Losses caused by tobacco 

 hornworms on tobacco are estimated to be about $35, 000, 000 annually. The amount 

 spent for their control by tobacco growers is difficult to estimate, but would probably 

 amount to $10, 000, 000 annually. 



The total acreage of tobacco and tomatoes east of the Mississippi River amounts 

 to about 1, 250, 000 acres. As mentioned elsewhere in this report, the writer has 

 estimated the natural population density for the spring brood to be of the order of 40 

 moths per acre. Based on actual field data obtained by F. R. Lawson and his associates 

 of the Oxford, N,C. laboratory, this estimate is probably high. To be conservative, 

 however, the basic population will be considered to be 40 moths per acre. Lawson and 

 associates estimate that through a fully coordinated fall program, based largely on 

 cultural control practices, it should be feasible to reduce the normal population by 80 

 percent. According to the basic assumption, this would mean an average of about 8 

 moths per acre for the spring brood, following the previous fall cultural program. If 

 8 moths per acre of host crops is a valid estimate, the total spring brood of moths 

 would consist of about 10, 000, 000 moths. 



If we assume that a population of hornworms under normal tobacco- growing 

 practices will increase at a five-fold rate per generation, it would be necessary to 

 overflood the natural population by more than 4 to 1 to start a downward population 

 trend. A 10:1 ratio will be established as the initial release rate. This would require 

 100 million moths for the first brood. 



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